JPH082505Y2 - Drum brake structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a drum brake structure mounted on a two-wheeled vehicle, a four-wheeled vehicle, or the like.

(Prior Art) In order to operate a drum brake mounted on a wheel of an automobile, there are a hydraulic type and a mechanical type, and some have two systems. In the hydraulic type, the oil in the oil tank flows into the brake pipe through the master cylinder, is supplied to the wheel cylinder, and the brake pedal is depressed,
It has a structure that hydraulic pressure is transmitted from the master cylinder to the wheel cylinders via the brake pipes.
In the mechanical type, a brake wire is connected to a hand brake lever and is connected to an extension lever attached to a wheel, and a piston in a wheel cylinder is mechanically moved.

The brake body has a back plate attached to the rear axle housing, which holds an arc-shaped brake shoe with a T-shaped cross section, and a lining attached to the outer periphery of the brake shoe. The wheel cylinder is attached to the end of the brake shoe. They are connected to each other, and the expansion force of the brake shoes presses the outer drum. This structure is called an internal expansion type.

As shown in FIG. 5, two brake shoes 2 formed in an arc shape having a T-shaped cross section are installed inside the cylindrical drum 1 so as to face each other, and a lining 3 is provided on a surface along the outer peripheral wall. Is installed so that it can be replaced. The brake shoe 2 is held by the back plate 4 from the inside of the vehicle body, the outer peripheral edge of the back plate 4 is bent toward the drum 1 side, and is aligned with the groove formed at the end portion of the outer peripheral wall of the drum 1 on the back plate 4 side. There is. Since the distance m between the brake shoe 2 and the drum 1 influences how well the brake works, an adjusting mechanism is provided so that it can be adjusted. When viewed from a wheel cylinder (not shown) attached to the back plate 4, the first shoe is called the primary shoe and the other shoes are called secondary shoes in the rotation direction (forward movement) of the drum 1. If so, both shoes become primary shoes and strong braking force is obtained in one direction.

As described above, the sliding contact surface between the drum 1 and the brake shoe 2 is important, and the drum 1 is prevented from entering dust and water.
The gap space is bent at the matching position between the outer peripheral edge of the and the back plate 4 so that it cannot easily enter. Further, Japanese Utility Model Laid-Open No. 60-47661 discloses a drum having a hole formed on the outer periphery thereof to communicate with the outside in a gap formed by a rim and a waterproof plate so as to prevent foreign matter from being retained.

(Problems to be solved by the invention) However, the internal expansion type drum brake of the mechanism shown in FIG. 5 has a cylindrical outer peripheral wall, and therefore, when dust, rust, muddy water, or the like enters the structure, It is difficult to return to the gap that has entered, it easily remains in the drum,
Therefore, if it is sandwiched between the drum 1 and the brake shoe 2, the sliding contact surface is reduced, the braking performance is deteriorated, and the parts are damaged and the life is shortened.

An object of the present invention is to provide a drum brake structure for keeping the inside of the drum clean and maintaining the braking performance.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a structure of a drum brake in which a brake shoe is spread to abut against the inside of a drum and the frictional force is applied to brake the drum, and the drum is substantially conical. It is formed in a trapezoidal shape, a spiral groove that opens to the outside is provided on the tapered inner peripheral surface of the drum, and the brake shoe is provided with a lining having a tapered surface along the inner peripheral surface. Is characterized by.

(Effect) With the above-described configuration of the present invention, when the brake shoe is operated to the outer peripheral side, the tapered surface of the lining is brought into sliding contact with the inner surface of the drum during a brake operation, so that a normal braking force can be obtained. Further, when dust is mixed between the drum and the lining, the spiral groove crosses in the rotation direction, so the dust rolls into the groove and is moved to a gap communicating with the outside along the groove. It can be eliminated.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, a wheel 5 mounted on a vehicle is composed of a tire 6 and a wheel 7, and is made rollable by fastening a wheel 7 to a shaft 9 to which a drum 8 is fastened by bolts 10. The shaft 9 is inserted into and supported by a housing 12 with a bearing 11 interposed therebetween, and facilitates rotation of the shaft 9. A flange 13 is formed at the front end of the housing 12 and a mounting hole 13a is formed therein to mount an annular back plate 14.

As shown in FIGS. 1 and 2, the back plate 14 has a hole 14a for the shaft 9 in the center and a hole 14b for mounting the housing 12 in the periphery. Further, an edge portion 14c bent outwardly of the vehicle body is formed on the outer periphery so as to be aligned with the drum 8. The back plate 14 holds two arcuate brake shoes 15 each having a T-shaped cross section, and is provided so as to be expandable outward by a wheel cylinder 18 provided with an adjusting lever 16 and an adjusting spring 17. In addition, the brake shoe 15 has a return spring.
19 is attached to stabilize the position. A lining 20 is stretched around the outer peripheral surface of the brake shoe 15.

By the way, as shown in FIGS. 1 and 3, one end of the cylindrical drum 8 is connected to the outer peripheral portion of the back plate 14, and the other end is formed by a mounting hole 8b formed around a hole 8a opened at the center.
It is fastened together with the shaft 9 with bolts 10. The inner peripheral surface 8c of the side wall of the drum 8 is formed in a tapered shape in which the shaft 9 side has a small diameter and is formed in a substantially truncated cone shape. Further, a groove 8d is formed at the end portion of the inner peripheral surface 8c on the pack plate 14 side to align with the edge portion 14c of the pack plate 14, and a spiral groove 8e is formed on the inner peripheral surface 8c to form a spiral shape. The tip of the groove 8e is open to the outer circumference. Therefore, the brake shoes 15
The contact surface has a groove 8e, which is inclined with respect to the axis and is lined.
The surface of 20 is also adjusted to the inclination of the inner peripheral surface 8c of the drum 8.
The groove 8e can be formed by a cutting machine or the like.

 Next, the operation will be described.

First, operate the wheel cylinder 18 with hydraulic pressure,
When the brake shoe 15 is expanded to the outside, the lining 20 contacts the inner peripheral surface 8c of the drum 8 and presses the drum 8 from the inside, so that a frictional force works and a braking force is obtained. Back plate
Abrasion debris, rust, mud, inside the 14 and drum 8
When dust such as water enters, the dust falls into the spiral groove 8e due to its own weight or centrifugal force, and the inner peripheral surface 8c
The contact surface of the brake shoe 15 is kept clean, and the dust is discharged to the outside of the drum 8 by the centrifugal force generated by the rotation of the drum 8. Further, when the lining 20 of the brake shoe 15 is pressed against the inner peripheral surface 8c of the drum 8, a phenomenon of biting into the spiral groove 8e occurs and the braking force increases.

Further, by providing the spiral groove 8e on the drum 8, the heat radiation area of the drum 8 is increased, which is advantageous for cooling.

Further, as shown in FIG. 4, four or more spiral grooves 8e may be provided inside the drum 8.

(Effects of the Invention) Since the present invention is configured as described above, the conventional cylindrical drum has a truncated cone shape and a spiral groove is provided to discharge dust. The inner surface of the drum can be cleaned, and the contact surface of the brake shoe can be made clean, and the life of the brake is long and stable and strong braking force can be obtained. Further, the structure is simple and the processing is easy, so that the cost can be reduced. Further, since the surface area of the groove is increased, a cooling effect can be obtained.

[Brief description of drawings]

1 is a side sectional view of a drum brake according to an embodiment of the present invention, FIG. 2 is a perspective view of a brake shoe side of a drum brake of the embodiment, and FIG. 3 is a perspective view of a drum side of a drum brake of the embodiment. FIG. 4 is an inner plan view of a drum of another embodiment, and FIG. 5 is a side sectional view of a conventional drum brake. 8 …… drum 8c …… inner peripheral surface 8e …… spiral groove 15 …… brake shoe 20 …… lining

Claims (1)

[Scope of utility model registration request] 1. A structure of a drum brake in which a brake shoe is spread and brought into contact with the inner side of a drum to brake by the frictional force thereof, wherein the drum is formed in a substantially truncated cone shape, and is formed in a taper shape of the drum. A drum brake structure characterized in that a spiral groove that opens to the outside is provided on an inner peripheral surface, and a lining having a tapered surface along the inner peripheral surface is provided on the brake shoe.